Which of the following best defines demand elasticity?

Demand elasticity refers specifically to how sensitive the quantity demanded of a good or service is to changes in its price. When the price of a product changes, demand elasticity measures the resulting effect on the quantity consumers are willing to buy. If demand is elastic, a small change in price will lead to a large change in the quantity demanded. Conversely, if demand is inelastic, changes in price have little effect on the quantity demanded.

Understanding this concept is crucial for businesses as it helps them make pricing decisions, anticipate consumer behavior, and strategize sales and marketing efforts. For example, if a product has elastic demand, lowering prices could significantly increase sales volume, while for products with inelastic demand, price reductions might not lead to substantial changes in sales.

The other options do not capture the essence of demand elasticity. Stability of prices relates more to market conditions than to consumer sensitivity to price changes. The effect of marketing on sales is a broader concept that encompasses various factors beyond just price. The proportion of fixed costs in pricing does not relate to how consumers respond to price fluctuations but rather to cost structure and pricing strategy.